June 27 (Bloomberg) -- A metric proposed as part of the
International Civil Aviation Organization’s plan to curb
greenhouse gases in the airline industry will mask the actual
emissions of aircraft, according to an aeronautical engineer.

The proposal uses a plane’s maximum take-off weight, a
certification level known as MTOW, to help determine emissions
and whether the aircraft is efficient enough to fly, said
Dimitri Simos, founder of Lissys Ltd., an airline-engineering
software company near Leicester, England, whose clients have
included Boeing Co. and Airbus. Lissys’s Piano software has been
approved under ICAO’s models for determining fuel burn.

“It is physically impossible to divine a meaningful weight
for CO2 assessments from certification restrictions alone, as
ICAO’s metric implicitly purports to do,” Simos said in a
statement on his website. “Using MTOW as a weight determinant
of CO2 is scientifically, and surely also legally under any
rational system, utterly indefensible.”

The United Nations-overseen organization is seeking to
finalize a greenhouse-gas-reduction plan after the European
Union from January for the first time included airlines in its
carbon market, the world’s biggest by traded volume. Europe can
replace its carbon curbs on aviation with a global measure as
long as the broader program is as ambitious as the EU plan,
Connie Hedegaard, the bloc’s climate chief, said Feb. 17.

ICAO needs to require airlines to use models that measure
actual emissions, which need to be based on metrics including an
aircraft’s operating empty weight, as well as its engine and
aerodynamic characteristics, Simos said.

“The ICAO approach is akin to selecting a basketball team
from the general population on the basis of height alone,” he
said today by e-mail. “Different aircraft emit CO2 differently
in transporting specific payloads over specific ranges.”

ICAO may have proposed its metric because aircraft
manufactures and airlines are reluctant to disclose the actual
fuel burn and efficiency of their planes, he said.

“They are not willing to give the real performance of
aircraft,” he said.